Plasminogen (alternatively known as microplasmin, PLG or angiostatin) is a single chain 91 kDa glycoprotein zymogen, and is the precursor of the fibrinolytic enzyme plasmin. The native form of plasminogen is composed of 791 amino acids with glutamic acid located at the N-terminal portion (Glu-plasminogen). Plasminogen has five homologous regions known as kringles. These regions are specific for the complimentary kringles located on tPA, uPA and prothrombin. These kringles have one high affinity and four low affinity lysine binding sites that mediate the interactions of plasminogen with fibrin and alpha-2-antiplasmin.
Plasminogen is converted to plasmin via a cascade of various reactions that result in the hydrolysis of the Arg560-Val561 peptide bond of plasminogen, resulting in two chains which remain covalently associated by a disulfide bond. The main role of the trypsin-like protease plasmin is the breakdown of clots.
Plasminogen deficiencies resulting from homo- or heterozygous mutations in the coding DNA manifest themselves in a number of pathologies, including ligneous conjunctivitis and thrombosis.
Plasminogen is present in human plasma at a concentration of ˜100 μg/mL. It is possible to purify the plasminogen from plasma using immobilised lysine on a solid support, in an affinity chromatography process that is well characterised. Immobilised lysine chromatography is also used for the primary capture from cell culture harvest of proteins such as tissue plasminogen activator (tPA), commonly used as a clot-busting drug. The binding capacities of commercially available resins for plasminogen are typically in the range 0.6-1.0 mg protein/mL of adsorbent. The purity of the plasminogen eluted from these materials is excellent, with purity routinely >95% from primary capture. It would be useful to have a material retaining these characteristics of excellent elution purity, but displaying a binding capacity in excess of those currently available.
WO97/10887 discloses triazine-based compounds, useful as affinity adsorbents, of formula I
wherein R1 is H, alkyl, hydroxyalkyl, cyclohexyl, NH2, phenyl, naphthyl, 1-phenylpyrazole, indazole, benzthiazole, benzoxazole or benzimidazole, any of which aromatic groups can be substituted with one or more of alkyl, alkoxy, acyloxy, acylamino, amino, NH2, OH, CO2H, sulphonyl, carbamoyl, sulphamoyl, alkylsulphonyl and halogen;
one X is N and the other is N, C—Cl or C—CN;
Y is O, S or NR2;
Z is O, S or NR3;
R2 and R3 are each H, alkyl, hydroxyalkyl, benzyl or β-phenylethyl;
Q is benzene, naphthalene, benzthiazole, benzoxazole, 1-phenylpyrazole, indazole or benzimidazole;
R4, R5 and R6 are each H, OH, alkyl, alkoxy, amino, NH2, acyloxy, acylamino, CO2H, sulphonic acid, carbamoyl, sulphamoyl, alkylsulphonyl or halogen;
n is 0 to 6;
p is 0 to 20; and
A is a support matrix, optionally linked to the triazine ring by a spacer.
Compounds of formula I are disclosed as having affinity for proteins such as immunoglobulins, insulin, Factor VII or human growth hormone.
Compounds of related structure are disclosed in WO00/67900 and WO03/097112. They have affinity for endotoxins.